US President Donald Trump has weighed in amid speculation that embattled British Prime Minister Sir Keir Starmer will announce his resignation on Monday (local time).

Starmer is struggling with some of the lowest popularity ratings for any British PM in modern political history.

“Keir Starmer will resign as ​Prime ​Minister of The United Kingdom,” ‌Trump ⁠wrote on Truth Social.

“He failed badly ​on ​two ⁠very important subjects – IMMIGRATION ​AND ENERGY (OPEN NORTH ​SEA ⁠OIL!). I wish him ⁠well!”

An expected rival for the Labour leadership, Andy Burnham, won a decisive byelection victory on Friday, prompting more Labour ministers to call for Starmer to go.

Dozens of MPs and some ministers have privately called for him to set out a timetable for his departure to clear the way for the former Greater Manchester mayor when he returns to parliament.

A source with knowledge of the matter said Starmer spent the weekend thinking about and discussing his position with his family. An expected conversation with Burnham would clarify matters.

“Keir ‌likes to think about ‌things,” the source said.

Starmer’s unpopularity was laid bare by Labour’s heavy losses in local elections in May, and polls of party members indicate Burnham would win a formal leadership contest.

Should Burnham take over, he would become Britain’s seventh prime minister in the past 10 years.

Sky News reported that it understood foreign minister Yvette Cooper had called on Starmer to stand down in a private conservation over the ⁠weekend.

Her spokesperson did not immediately respond to a request for comment.

Her apparent appeal, alongside other ‌ministers and dozens ​of MPs, increased the sense that it is a case of when rather than if Starmer will step aside.

Starmer said only a few days ago that he would ​stand in any formal ‌Labour leadership contest that sought to replace him.

While Starmer’s team believes his landslide general election win in 2024 gives him the mandate to stay in his post ​until 2029, business minister Peter Kyle said the PM was reflecting on the “the political challenges that he faces in this moment”.

Kyle said he spoke to Starmer on Friday, finding a man who was questioning what “the country expected of him”. The conversation showed Starmer was in “very difficult circumstances”, he said.

“​I’m ​not going to deny the political challenges that he faces in this ​moment but what I’m also not going to do is say there is ever anything ‌inevitable about the days ahead,” Kyle told LBC radio.

He told the BBC he didn’t know “what’s going to unfold in the days that lie ahead”.

“I don’t know the decisions that he will make on behalf of our country as he considers these issues, and then makes decisions,” he said.

“But we will find a way for this to be whatever unfolds, a functional process, one where the Labour Party is seen to put the interests of the country first and foremost, and we will carry on delivering for this country through whatever does unfold in the days ahead.”

Burnham’s thumping win over the populist Reform UK party to take a parliamentary seat in Makerfield prompted more MPs and ministers to press Starmer to set a timetable for his departure to avoid what could be a divisive leadership race.

The team supporting Burnham, a 56-year-old career politician, had said it was giving Starmer the weekend to consider his position in the hope that he would set out an orderly transfer of power. As yet, there is no ​indication the two have spoken.

Former minister Jess Phillips – a supporter of health secretary Wes Streeting, another potential challenger to Starmer – told the BBC that “it feels ​like we’ve come to the end of ⁠the road” and that it would be best for Starmer’s departure to be “as dignified as possible”.

Starmer’s office said on Sunday that his position remained unchanged from Friday, when he said he will not “walk away” from Downing Street and will stand in any potential leadership contest.

-with AAP/PA